Device For Vibration-Free Mounting Of A Spindle In A Stand Of A Surgical Microscope

ABSTRACT

A device for mounting a drive shaft driven by a drive motor is described, in which device a carriage is driven via the drive shaft. The drive motor is embodied as a stepper motor ( 1 ), and the drive shaft ( 6 ) is joined to the carriage ( 8; 9 ) via an elastomeric damper ( 3 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of German patent application 10 2006 040 868.3 filed Aug. 31, 2006 and German patent application 10 2006 044 469.8 filed Sep. 21, 2006, both of which are incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a device for vibration-free mounting of a drive shaft, such as a threaded spindle, to a carriage. The invention finds particular application in an X-Y displacement unit for mounting a surgical microscope on a stand.

BACKGROUND OF THE INVENTION

The purpose of the stands of a surgical microscope is on the one hand to hold the microscopes securely, and on the other hand to ensure counterbalanced positioning of the surgical microscope. This counterbalancing is usually achieved by way of displaceable counterweights so that, despite changeable loads, the microscope is easily positionable in three dimensions.

DE 43 20 443 A1 discloses a stand for a surgical microscope that uses displaceable weights for weight compensation. Also presented in this document is a motorized X-Y positioning unit that is arranged on the stand and carries the surgical microscope. The motorized X-Y positioning unit comprises two carriages that are embodied movably via a DC motor and a linkage. This X-Y positioning unit is evidently used in this document to carry out an automatic fine balancing of the surgical microscope.

An X-Y positioning unit of this kind can also be used in a counterbalanced microscope or stand to move the surgical microscope over the surgical site in the X and Y directions so as thereby to establish a different image area during the operation.

The existing solution provides, for such displacement by an X-Y positioning unit, DC motors having an encoder and linkage. These solutions have proven to function well, but because of the many components are very complex and of correspondingly large dimensions. The linkages furthermore cause noise, which has been reduced by way of so-called solid-borne sound dampers. An apparatus for securing a solid-borne sound-transferring component is depicted and described in DE 10 2005 014 376 (not previously published).

Previous attempts to replace the DC motors having a separate linkage and encoder with stepper motors of simple construction having an integrated spindle or drive shaft failed because the individual steps of the motors resulted in a jerky motion in the image. Jerky motions in the image are, however, unacceptable to a surgeon. The jerky motion furthermore causes an oscillation of the moving mass and consequently an excitation of the system, in particular of the microscope. The microscope, weighing approximately 15 kg, begins to oscillate slowly, and the result is an unstable image for the surgeon. The microscope continues to oscillate even after the stepper motor is shut off. This has proven to be unusable in practice.

SUMMARY OF THE INVENTION

It is an object of the present invention to enable the use of stepper motors having a drive shaft, and thereby to eliminate the disadvantages referred to above.

This object is achieved by the invention described herein.

The invention is notable for the fact that the drive shaft of the stepper motor is joined to the carriage via at least one elastomeric damper. The result of this is that no direct connection exists between the drive shaft and the carriage, and vibrations and other disruptions are dissipated by the technical spring or elastomeric damper.

The motion of the motor, i.e. at each individual step, causes a jerky motion of the drive shaft and thus also of the carriage. Without the elastomeric damper, these jerky motions are transferred as a pulse to the housing and microscope. With the elastomeric damper, these pulses are received and absorbed by the damper. No pulse transfer to the carriage therefore takes place, and oscillation of the carriage or the microscope is prevented.

An elastomeric damper having the aforementioned properties is marketed, for example, by the company styled Getzner Werkstoffe, Bürs/Bludenz, Austria.

In a further embodiment of the invention, the carriage comprises a flange in which the elastomeric damper is movably arranged, so that possible excursions of the drive shaft or spindle are compensated for by a displacement of the elastomeric damper in the flange.

In a refinement of the invention, the elastomeric damper is embodied as a washer that comprises a centered orifice for the drive shaft. This ensures secure retention of the drive shaft in the elastomeric damper.

In a further embodiment of the invention, multiple elastomeric dampers arranged next to one another are provided in order to enhance the damping properties.

In a further embodiment of the invention, the stepper motor having the drive shaft and the elastomeric bearing is provided as a drive for a zoom system in the surgical microscope, so that no vibrations are transferred to the stand or to the surgical microscope upon a change in magnification by adjustment of the zoom.

In a preferred embodiment of the invention, the stepper motor having the drive shaft and the elastomeric bearing is arranged as a drive in an X-Y displacement unit for the surgical microscope so as thereby to ensure vibration-free movement of the microscope over the surgical site even during the operation.

In a refinement of the invention, the stepper motor is equipped directly with a spindle, in particular a threaded spindle, so that an additional linkage is superfluous.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is schematically depicted in the drawings and will be described below in an exemplifying embodiment with reference to the Figures, in which:

FIG. 1 is a view of an X-Y carriage having stepper motors;

FIG. 2 shows the arrangement of the stepper motors in the carriage;

FIG. 3 is a sectioned depiction of the stepper motor with flange;

FIG. 4 shows a stand having a surgical microscope and X-Y displacement unit; and

FIG. 5 is a sectioned depiction of the second exemplifying embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a view of X-Y displacement unit 7 having a frame 11. Arranged on frame 11 is a linear guidance system 10 on which a carriage 8 movable in the X direction is mounted. A carriage 9 movable in the Y direction is arranged in equivalent fashion on the other side of frame 11. Associated with each of carriages 8, 9 is a receptacle 18 for a stand arm (not depicted) of a surgical microscope.

A stepper motor 1 having a drive shaft embodied as a threaded spindle 6 is provided to drive carriage 9. Stepper motor 1 is joined to a receiving flange 12. Receiving flange 12 is mounted on frame 11.

FIG. 2 is a view of X-Y displacement unit 7 with the stationary frame 11 and with stepper motors 1 for carriage 8 and carriage 9 (not visible in FIG. 2). Stepper motor 1 is joined to receiving flange 12.

For each direction, spindle 6 of stepper motor 1 is retained in a spindle guide 13 that is joined to a flange 2 as a drive for the associated carriage 8 or 9. A rotation of spindle 6 by stepper motor 1 is thus converted into a linear motion of the associated carriage.

FIG. 3 is a section through spindle guide 13, with flange 2 in which an elastomeric damper 3 is retained via a flange 2 a. Elastomeric damper 3 is arranged in clamped fashion between two washers 14 so as to result in a preload for elastomeric damper 3 of at least 6% of its volume. Spindle 6 of stepper motor 1 is guided through an orifice 4 in elastomeric damper 3 and through the two washers 14, and is equipped at the end with a nut 5 and a sleeve 20. The clamping of elastomeric damper 3 is accomplished via nut 5, sleeve 20, and the two washers 14. Elastomeric damper 3 may be made of a mixed cell polyurethane sold by Getzner Werkstoffe under the designation SYLODAMP HD 300.

FIG. 4 schematically shows a stand 15 with a counterweight 16 and a surgical microscope 17 that is secured via X-Y displacement unit 7 on the stand. The image area of surgical microscope 17 can be modified by way of X-Y displacement unit 7.

FIG. 5 shows a further exemplifying embodiment of spindle guide 13 having two elastomeric dampers 3 arranged parallel to one another, which are clamped between flange 2 and the two washers 14. For this, nut 5 is associated with spindle 6 so that a nonpositive connection between the two elastomeric dampers 3 and flange 2 is generated by tightening screw 5. The two elastomeric dampers are, in this context, compressed by at least 6% of the initial volume. Flange 2 has at the center an orifice 19 for the passage of spindle 6, and is joined directly to carriage 8.

PARTS LIST

-   -   1 Stepper motor     -   2 Flange     -   2 a Flange     -   3 Elastomeric bearing     -   4 Orifice     -   5 Nut     -   6 Drive shaft; spindle     -   7 X-Y displacement unit     -   8 Carriage     -   9 Carriage     -   10 Linear guidance system     -   11 Frame     -   12 Receiving flange     -   13 Spindle guide     -   14 Washer     -   15 Stand     -   16 Counterweight     -   17 Surgical microscope     -   18 Receptacle     -   19 Orifice     -   20 Sleeve 

1. A device comprising: a stepper motor; a drive shaft driven by the stepper motor; a carriage driven by the drive shaft; and at least one elastomeric damper; wherein the drive shaft is connected to the carriage via the at least one elastomeric damper.
 2. The device according to claim 1, wherein the carriage includes a flange in which the at least one elastomeric damper is arranged.
 3. The device according to claim 1, wherein the at least one elastomeric damper includes an orifice through which the spindle extends.
 4. The device according to claim 1, wherein the at least one elastomeric damper is embodied as a washer.
 5. The device according to claim 2, wherein the at least one elastomeric damper includes a plurality of elastomeric dampers.
 6. The device according to claim 5, wherein the plurality of elastomeric dampers are arranged next to one another.
 7. The device according to claim 5, wherein the plurality of elastomeric dampers includes at least two elastomeric dampers nonpositively joined to the flange by at least two washers.
 8. The device according to claim 1, wherein the drive shaft is embodied as a threaded spindle.
 9. The device according to claim 1, wherein the at least one elastomeric damper is installed with a preload of at least 6% of its original volume.
 10. An X-Y displacement unit for positioning a surgical microscope along orthogonal X and Y directions, the X-Y displacement unit comprising: a frame; a first stepper motor and a second stepper motor each mounted on the frame; a first drive shaft extending in the X direction, the first drive shaft being rotated by the first stepper motor; a second drive shaft extending in the Y direction, the second drive shaft being rotated by the second stepper motor; a first carriage connected to the first drive shaft for travel in the X direction; a second carriage connected to the second drive shaft for travel in the Y direction; a first elastomeric damper, the first drive shaft being connected to the first carriage via the first elastomeric damper; and a second elastomeric damper, the second drive shaft being connected to the second carriage via the second elastomeric damper.
 11. The X-Y displacement unit according to claim 10, wherein the first and second drive shafts are threaded spindles directly driven by the first and second stepper motors, respectively.
 12. A surgical microscope comprising: a zoom system having at least one movable lens; a stepper motor; a drive shaft rotated by the stepper motor and coupled to the at least one movable lens, the stepper motor being operable to move the at least one movable lens to adjust magnification of the zoom system; and at least one elastomeric damper, the drive shaft being connected to the at least one movable lens via the at least one elastomeric damper. 